The genus Phlebovirus is one of five genera of the Bunyaviridae family. Phleboviruses are enveloped spherical viruses with icosahedral symmetry. The genome of Phleboviruses consists of three single-stranded RNA genome segments—small (S), medium (M) and large (L). The M and L segments use a negative sense coding strategy, while the S segment encodes two proteins using an ambisense strategy. The S segment encodes the non-structural protein NSs in the positive sense orientation and the nucleoprotein (NP) in the negative sense orientation; each protein is translated from a subgenomic virus mRNA. The M segment encodes the glycoprotein precursor that is cleaved by host proteases into two structural domains—Gn and Gc. The L segment encodes the L protein, which functions as the RNA dependent RNA polymerase in primary and secondary transcription to generate mRNA and replicative intermediates, respectively.
There are approximately 70 named viruses in the Phlebovirus genus. These viruses are classified based on their serological relationships into two antigenic groups, the phlebotomus or sandfly fever group and the Uukuniemi group (Nichol et al., Virus Taxonomy: Classification and Nomenclature of Viruses. Eighth Report of the International Committee of the Taxonomy of Viruses. Elsevier Academic Press, Genus Phlebovirus, pp. 706-716, 2005). Phleboviruses have a worldwide distribution and are transmitted by a wide variety of arthropods, including sandflies, mosquitoes and ticks. Several Phleboviruses have been linked to human disease, in some cases causing febrile illness, fever, hepatitis, meningitis, encephalitis or hemorrhagic syndrome.
Ticks (Acari: Ixodidae) transmit bacterial and viral pathogens to humans in the United States and elsewhere. Lyme disease, rickettsioses, ehrlichioses, tularemia, babesiosis, and Powassan virus infections of humans have all increased over the last decade. Reasons for these increases are multifactorial and include improved diagnosis, climate effects, and changes in land use (Roche et al., First culture isolations of Ehrlichia chaffeensis from a Missouri patient. In: 22nd Annual Meeting of the Society for Vector Ecology. Ft. Collins, Colo., 2008). An important species of tick that can transmit numerous pathogens is the lone star tick, Amblyomma americanum. In many parts of the country, humans are regularly exposed to this species and the pathogens it may carry (Goddard and Varela-Stokes, Vet Parasitol 160:1-12, 2009; Paddock and Yabsley, Curr Top Microbiol Immunol 315:289-324, 2007).